I seem to have a disparity between what my net caloric loss is, versus what the weight scale is.

According to the site's information, I should have only burned 1.98lbs this week, yet I actually burned 4 lbs according to the scale. Is this simply the inaccuracy of the site to -truly- measure every iota of what I eat and burn? Seems odd that it would be off by 7,000 calories in a week!